Implement fma in soft-fp

[Joseph S. Myers]

On Tue, 25 Jun 2013, Richard Henderson wrote:

> Of course, that would require glibc to build parts with the c++ compiler,
> so that may be a non-starter...

And libgcc, and the Linux kernel - I don't think requiring a C++ compiler 
all over the place would be a good idea (and it would complicate 
bootstrapping - you can't build libstdc++ without system headers, but need 
to have built libgcc before building glibc, so a bootstrap compiler would 
need the C++ compiler and a subset of the runtime libraries).

It's possible something could be done simply with inline always_inline 
functions in C.  The code doesn't just predate SRA, it predates inlining 
on trees.  I think I once discussed that issue, for this code, of why 
inlines were less efficient than macros with GCC as it stood at that time, 
with Peter Maydell around 1997/8.

(But maybe things like getting access to exception / rounding mode state, 
which is in a local variable in the toplevel function, would complicate 
any such macro-avoidance scheme, including the C++ ones.)

-- 
Joseph S. Myers
joseph@codesourcery.com